Initialize render_frame_host_ in the constuctor of ServiceWorkerHandler.

content/browser/devtools/protocol/service_worker_handler.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/devtools/protocol/service_worker_handler.h"
 
 #include "base/bind.h"
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 212 matching lines @@
     case DevToolsAgentHost::TYPE_BROWSER:
       return "browser";
   }
   NOTREACHED() << type;
   return std::string();
 }
 
 }  // namespace
 
 ServiceWorkerHandler::ServiceWorkerHandler()
-    : enabled_(false), weak_factory_(this) {
+    : enabled_(false), render_frame_host_(nullptr), weak_factory_(this) {
 }
 
 ServiceWorkerHandler::~ServiceWorkerHandler() {
   Disable();
 }
 
 void ServiceWorkerHandler::SetRenderFrameHost(
     RenderFrameHostImpl* render_frame_host) {
   render_frame_host_ = render_frame_host;
   // Do not call UpdateHosts yet, wait for load to commit.
@@ skipping 344 matching lines @@
     return;
   host->DetachClient();
   client_->WorkerTerminated(WorkerTerminatedParams::Create()->
       set_worker_id(host->GetId()));
   attached_hosts_.erase(it);
 }
 
 }  // namespace service_worker
 }  // namespace devtools
 }  // namespace content